1) Field of the Invention
The present invention relates to a library apparatus which stores a large number of cartridges such as magnetic tape cartridges and optical disk cartridges, and which transfers the cartridges through an accessor to a deck for processing a storage medium accommodated within each of the cartridges.
2) Description of the Related Art
In general, a library apparatus functions as a large-capacity external storage memory, and a storage rack in its locker stores several thousands of cartridges each accommodating, for example, a magnetic tape as a storage medium, and access such as write/read of recording/recorded data is automatically done in relation to the storage medium within each of the cartridges.
Furthermore, the library apparatus is equipped with the aforesaid storage rack for storing the cartridges, a plurality of magnetic tape decks (which will be referred hereinafter to as decks) for conducting access such as write/read of recording/recorded data with respect to a storage medium (magnetic tape) within a cartridge, and an accessor (cartridge transferring robot) for performing the conveyance of the cartridges between the storage rack and the decks.
Commonly, this library apparatus is made up of a storage unit having a storage rack for storing a large number of cartridges, a drive unit incorporating decks, an accessor unit functioning as a garage for accessors, a unit including a controller or the like for controlling the accessors, and other units.
Each of these units is constructed as being one locker, and the arrangement of the whole library apparatus relies on the connections among a plurality of lockers (units). In addition, with the plurality of lockers being in connection, a traveling passage for the accessors is defined in these lockers to penetrate them.
In the library apparatus thus arranged, in response to an access request to one cartridge from a host unit or the like, the accessor travels within the passage to come to the storage rack to search a directing cartridge there, and subsequently, a hand mechanism grips that cartridge and transfers it to the deck for insertion into the deck.
With these operations, in that deck, given processing is done with respect to the storage medium (magnetic tape) within the inserted cartridge. After the completion of the processing, the cartridge discharged from the deck is again gripped by the hand mechanism and conveyed by the accessor up to the storage rack to be stored at a given position.
In a prior library apparatus, a dedicated cartridge delivering and receiving mechanism is installed in each of the decks so that the insertion of the cartridge into the deck or the extraction (pulling-out) of the cartridge from the deck is carried out through the cartridge delivering and receiving mechanism. In this case, the accessor does not directly carry out the insertion/extraction of the cartridge into/from the deck.
However, recently, in order to accomplish the size and cost reduction of the library apparatus, is the accessor is capable of directly carrying out the insertion/extraction process into/from the deck without the use of the cartridge delivering and receiving mechanism. For meeting this requirement, in addition to achieving a higher control accuracy of the hand mechanism of the accessor, a high-accuracy positioning operation to the deck is required, and an error correction in the initial step (initial operation) is essential.